Monte Carlo simulations of geosynchrotron radio emission from CORSIKA-simulated air showers

We present simulations performed with REAS2, a new Monte Carlo code for the calculation of geosynchrotron radio emission from extensive air showers. The code uses thoroughly tested time-domain radio emission routines in conjunction with a realistic air shower model based on per-shower multi-dimensional CORSIKA-generated histograms. We assess in detail how the transition from simpler, parametrised, to realistic, CORSIKA-based particle distributions affects the predicted radio emission from a typical 10^17 eV air shower. The effects of eliminating a previously needed free parameter and adopting realistic electron to positron ratios are also discussed. Compared with earlier calculations based on parametrised showers, REAS2 simulations predict slightly weaker and in some cases narrower pulses. In addition, a pronounced east-west versus north-south asymmetry arises in the emission pattern, and the radio pulses become generally unipolar. Finally, we demonstrate how REAS2 can be used to study radio pulse shapes and their relation to shower characteristics such as the longitudinal air shower development.